OracleVM 3.3 : xen (OVMSA-2015-0095)

high Nessus Plugin ID 85037
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Synopsis

The remote OracleVM host is missing one or more security updates.

Description

The remote OracleVM system is missing necessary patches to address critical security updates :

- ide: Clear DRQ after handling all expected accesses This is additional hardening against an end_transfer_func that fails to clear the DRQ status bit. The bit must be unset as soon as the PIO transfer has completed, so it's better to do this in a central place instead of duplicating the code in all commands (and forgetting it in some).

This is XSA-138 CVE-2015-5154 (CVE-2015-5154)

- ide/atapi: Fix START STOP UNIT command completion The command must be completed on all code paths. START STOP UNIT with pwrcnd set should succeed without doing anything.

This is XSA-138 CVE-2015-5154 (CVE-2015-5154)

- ide: Check array bounds before writing to io_buffer (CVE-2015-5154) If the end_transfer_func of a command is called because enough data has been read or written for the current PIO transfer, and it fails to correctly call the command completion functions, the DRQ bit in the status register and s->end_transfer_func may remain set.
This allows the guest to access further bytes in s->io_buffer beyond s->data_end, and eventually overflowing the io_buffer. One case where this currently happens is emulation of the ATAPI command START STOP UNIT. This patch fixes the problem by adding explicit array bounds checks before accessing the buffer instead of relying on end_transfer_func to function correctly.
Cc :

This is XSA-138 (CVE-2015-5154)

- ide: Clear DRQ after handling all expected accesses This is additional hardening against an end_transfer_func that fails to clear the DRQ status bit. The bit must be unset as soon as the PIO transfer has completed, so it's better to do this in a central place instead of duplicating the code in all commands (and forgetting it in some).

This is XSA-138 (CVE-2015-5154)

- ide: Check array bounds before writing to io_buffer If the end_transfer_func of a command is called because enough data has been read or written for the current PIO transfer, and it fails to correctly call the command completion functions, the DRQ bit in the status register and s->end_transfer_func may remain set. This allows the guest to access further bytes in s->io_buffer beyond s->data_end, and eventually overflowing the io_buffer.
One case where this currently happens is emulation of the ATAPI command START STOP UNIT. This patch fixes the problem by adding explicit array bounds checks before accessing the buffer instead of relying on end_transfer_func to function correctly. Cc :

This is XSA-138 (CVE-2015-5154)

- tools: libxl: Explicitly disable graphics backends on qemu cmdline By default qemu will try to create some sort of backend for the emulated VGA device, either SDL or VNC. However when the user specifies sdl=0 and vnc=0 in their configuration libxl was not explicitly disabling either backend, which could lead to one unexpectedly running. If either sdl=1 or vnc=1 is configured then both before and after this change only the backends which are explicitly enabled are configured, i.e. this issue only occurs when all backends are supposed to have been disabled. This affects qemu-xen and qemu-xen-traditional differently.
If qemu-xen was compiled with SDL support then this would result in an SDL window being opened if $DISPLAY is valid, or a failure to start the guest if not.
Passing '-display none' to qemu before any further

-sdl options disables this default behaviour and ensures that SDL is only started if the libxl configuration demands it. If qemu-xen was compiled without SDL support then qemu would instead start a VNC server listening on ::1 (IPv6 localhost) or 127.0.0.1 (IPv4 localhost) with IPv6 preferred if available. Explicitly pass '-vnc none' when vnc is not enabled in the libxl configuration to remove this possibility. qemu-xen-traditional would never start a vnc backend unless asked. However by default it will start an SDL backend, the way to disable this is to pass a -vnc option. In other words passing '-vnc none' will disable both vnc and sdl by default.
sdl can then be reenabled if configured by subsequent use of the -sdl option. Tested with both qemu-xen and qemu-xen-traditional built with SDL support and: xl cr # defaults xl cr sdl=0 vnc=0 xl cr sdl=1 vnc=0 xl cr sdl=0 vnc=1 xl cr sdl=0 vnc=0 vga='none' xl cr sdl=0 vnc=0 nographic=1 with both valid and invalid $DISPLAY. This is XSA-119 / CVE-2015-2152. (CVE-2015-2152)

Solution

Update the affected xen / xen-tools packages.

See Also

https://oss.oracle.com/pipermail/oraclevm-errata/2015-July/000343.html

Plugin Details

Severity: High

ID: 85037

File Name: oraclevm_OVMSA-2015-0095.nasl

Version: 2.6

Type: local

Published: 7/28/2015

Updated: 1/4/2021

Dependencies: ssh_get_info.nasl

Risk Information

VPR

Risk Factor: Medium

Score: 6.5

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.3

Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C

Temporal Vector: E:U/RL:OF/RC:C

Vulnerability Information

CPE: p-cpe:/a:oracle:vm:xen, p-cpe:/a:oracle:vm:xen-tools, cpe:/o:oracle:vm_server:3.3

Required KB Items: Host/local_checks_enabled, Host/OracleVM/release, Host/OracleVM/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 7/27/2015

Vulnerability Publication Date: 3/18/2015

Reference Information

CVE: CVE-2015-2152, CVE-2015-5154

BID: 73068